ABSTRACT Positional cloning to identify the genes responsible for disease or particular traits involves mapping of the susceptibility locus through genome-wide association studies in humans and phenotypic analysis of recombinant strains and back-crossing in mice. Then responsible genes within such loci are identified based on their expression patterns, biochemical activities of the gene products and phenotypes of the corresponding knockout animal models. Unfortunately, the large size of susceptibility loci (usually >5 Mb) makes the downstream investigative steps rather challenging. The only way to narrow down the responsible region so far was to back- cross the carrier mice in order to trim the locus by homologous recombination. However, the chance of spontaneous recombination is very low, and trimming the locus to a manageable size is usually not feasible. We propose to develop the approach to artificially induce recombination at defined locations within the susceptibility locus (targeted recombination). This will provide the reliable route to pinpoint the causative mutations and ultimately, the mechanism of the disease in question.